power: supply: wm831x_power: fix spelling mistake on function name

There is a spelling mistake in the name wm831x_battey_apply_config,
fix it.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>